MINOR: docs typo in '--zookeeper myhost:2181--execute'

this PR will fix a typo related to docs:
http://kafka.apache.org/21/documentation.html#rep-throttle

```bash
$ bin/kafka-reassign-partitions.sh --zookeeper myhost:2181--execute --reassignment-json-file bigger-cluster.json —throttle 50000000
```

I think `myhost:2181` should be `localhost:2181` and followed by a `space`

Author: opera443399 <[email protected]>

Reviewers: Gwen Shapira

Closes apache#6704 from opera443399/docs-ops-typo

Author: opera443399

docs/ops.html

@@ -453,7 +453,7 @@ <h4><a id="rep-throttle" href="#rep-throttle">Limiting Bandwidth Usage during Da
   There are two interfaces that can be used to engage a throttle. The simplest, and safest, is to apply a throttle when invoking the kafka-reassign-partitions.sh, but kafka-configs.sh can also be used to view and alter the throttle values directly.
   <p></p>
   So for example, if you were to execute a rebalance, with the below command, it would move partitions at no more than 50MB/s.
-  <pre class="brush: bash;">$ bin/kafka-reassign-partitions.sh --zookeeper myhost:2181--execute --reassignment-json-file bigger-cluster.json —throttle 50000000</pre>
+  <pre class="brush: bash;">$ bin/kafka-reassign-partitions.sh --zookeeper localhost:2181 --execute --reassignment-json-file bigger-cluster.json —throttle 50000000</pre>
   When you execute this script you will see the throttle engage:
   <pre class="brush: bash;">
   The throttle limit was set to 50000000 B/s